Real-Time Color Doppler Radar Display

Abstract

Color enhancement of images has become a powerful tool in rapid evaluation of grey-scale information. Recent advances in semiconductor technology have made possible the construction of an inexpensive digital realtime color-enhanced (or false-color) display for meteorological radar information such as reflectivity and Doppler velocities. Variable magnification allows detailed analysis of selected areas of the radar coverage. The display was interfaced to a Doppler/reflectivity processor on the NHRE S-band radar at Grover, Colorado, during the 1974 hail season. A preliminary meteorological analysis of the Doppler color displays of the storm of 7 August 1974 demonstrates a large variety of significant features which may be observed either in real-time or subsequently. These include the regions of convergence and vorticity, major inflow and outflow regions, and turbulence. Most importantly, it is shown that the updraft cores can be identified with the easterlymomentum air which has been transported upward with the drafts from the lower levels. In view of the slow eastward motion of the storm system, the very large Doppler components found at the leading edge of the higher-level echo pattern also indicate rapid evaporation of the particles as they move out into the clear, dry environmental air. It is the resulting evaporative cooling which is responsible for the downdrafts in this vicinity. Among the many real-time applications of the color Doppler display, perhaps the most important in the artificial modification of convective storms is the location of the major inflow and updraft regions. These determine where seeding should be focused. The use of the color display also permits the ready discrimination of storm echoes from ground clutter in which they are frequently obscured. Its applicability to the detection of tornado cyclones and hurricane velocity mapping is also self-evident.

Use of Digital Radar Data in Severe Weather Forecasting

“…The development of Doppler weather radars (Gray et al, 1975) that can detect tornado vortices presents an exciting opportunity to develop very effective tornado warning systems. As in the case of the visual sightings, the Doppler radar can detect the phenomenon itself, and it has the advantages that the incipient tornadoes can be detected aloft well before touching ground (Donaldson, 1975), and detection can be made both day and night.…”

PATH TO NEXRAD: Doppler Radar Development at the National Severe Storms Laboratory

“…The mean velocity processor of Sirmans and Doviak (1973), with its coarse black-and-white display, was based on the pulse-pair concept. The second advance was the development of color monitors for displaying Doppler radar data (e.g., Jagodnik et al 1975;Gray et al 1975). The finer resolution provided by the use of color greatly improved the capability of observers to interpret reflectivity, mean Doppler velocity, and spectrum-width measurements in severe storms.…”

The Multiple Doppler Radar Workshop, November 1979

“…At NOAA's National Severe Storms Laboratory (Zahrai, 1980) and the National Center for Atmospheric Research (Gray et al, 1975), color display systems used to display data in real time are also used to observe recorded data in near-real time. Ideally such systems, in their real-time mode, should use read-after-write recording so that the data are always displayed as they are recorded on tape.…”

“…Thus, spectral variance is also used to threshold velocity. In the NCAR processing scheme spectral variance is not recorded, but a closely related quantity (amplitude of the complex autocorrelation function) is used in real time to set a good/bad velocity flag that is recorded and that is set whenever the coherence exceeds a preset value (Gray, 1975).…”